The surge in fighting between pro-Turkish rebels and Kurdish-aligned forces in northern Syria is "unacceptable" and must stop, the US has warned.

Clashes in places where Isil was not present were a "source of deep concern", the US envoy to the anti-Isil coalition tweeted.

Turkish forces have attacked what they say are Kurdish "terrorists" since crossing the border last week.

But the Kurdish YPG militia says Turkey just wants to occupy Syrian territory.

Ankara says it aims to push both Isil and Kurdish fighters away from its border.

Turkish forces and allied factions of the rebel Free Syrian Army (FSA) forced Isil out of the Syrian border city of Jarablus last week and have since pounded neighbouring villages held by Kurdish-led, US-backed Syria Democratic Forces (SDF).

The Turkish military carried out 61 artillery strikes around Jarablus over the past 24 hours, Reuters news agency reported yesterday.

Turkey, led by President Tayyip Erdogan, has insisted the Kurdish militia, which it regards as terrorists, retreat east across the Euphrates river.

Dozens of civilians were killed in Turkish airstrikes on Kurdish-held areas in Syria on Sunday, as the West's two main allies in the conflict inched closer to full-blown war.

Some 35 people died in dawn raids on Jeb el-Kussa and Al-Amarneh, villages close to the Turkish border.

Ankara, which has the support of the US, claimed they were "terrorists" from outlawed Kurdish militias.

The Jarablus Military Council, which is allied with the Kurdish-led Syrian Democratic Forces (SDF), said the strikes marked an "unprecedented and dangerous escalation".

Turkey also suffered its first casualty in Operation Euphrates Shield after an attack by Kurdish fighters left one soldier dead and three injured.

The Kurdish Popular Protection Units (YPG), which dominates the SDF, says its forces have withdrawn, and that the Turkish action against the group was a "pretext" for occupying Syria.